What are checkpoints?

[jukka]

With some wallets you sometimes see a warning that "checkpoint too old" and with some coins the new wallet contains "the latest check points"?

Could somebody explain me what are these checkpoints?

[stevegreer]

The way I understand it, and the simplest way to explain it, is that checkpoints are kinda like saves in a game (sorry, I'm not a gamer, so I don't know exactly what it is called). A checkpoint is a certain point in the blockchain that is saved which will allow all users to revert to in the case of something like a 51% attack so they don't lose too much of the blockchain. Maybe someone can explain it better, but that's how I understand it.

[jukka]

Does anybody have more specific explanation?

[Joe_Bauers]

The way I understand it, and the simplest way to explain it, is that checkpoints are kinda like saves in a game (sorry, I'm not a gamer, so I don't know exactly what it is called).

Funny enough, saves in a game are usually called..... checkpoints 

As for the description:  https://en.bitcoin.it/wiki/Checkpoint_Lockin

[jukka]

The way I understand it, and the simplest way to explain it, is that checkpoints are kinda like saves in a game (sorry, I'm not a gamer, so I don't know exactly what it is called).

Funny enough, saves in a game are usually called..... checkpoints 

As for the description:  https://en.bitcoin.it/wiki/Checkpoint_Lockin

Thanks, will go thru these...

[stevegreer]

Does anybody have more specific explanation?

Jeez, sorry guy. Made it too simple for you did I?

[PereguineBerty]

@stevegreer

What you posted was an excellent simile which was perfect for somebody who didn't seem able to use Google or the search function in here.

[jukka]

Does anybody have more specific explanation?

Jeez, sorry guy. Made it too simple for you did I?

I littlebit, but thanks anyway! I appreciate it!

[stevegreer]

@stevegreer

What you posted was an excellent simile which was perfect for somebody who didn't seem able to use Google or the search function in here.

Thanks!

@jukka, I was just messing with you. I wasn't offended at all. 

[r0ach]

Bitcoin uses checkpoints to stop people from creating low difficulty side chains as an annoyance/attack vector.  PoS coins use it to stop block chain reorgs in general.

[YarkoL]

Yep.. the "offficial" reason for
checkpoints is to ward off situation where someone starts to mine either mistakenly or maliciously
low difficulty blocks, thus forking the earlier part of the chain.

The presence of checkpoints enable other clients to reject these forked blocks and not waste time storing
and processing them.  

More info here
https://bitcointalk.org/index.php?topic=194078.0

[jukka]

Thank you everybody!